Poly-pen is a graphical proxy for Common Lisp. It links hi-level plotting operations to low-level back-ends graphics library. It offers a simple interface to image generation and a few hi-level operations like plots and color maps. You can find example images with the generation code in the
user manual. Current back-ends are for CL-SDL, CL-GD, Skippy and Salza(PNGs). Fract, the web zoomer for the Mandelbrot Set uses poly-pen for its rendering.